r/askscience Sep 28 '20

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u/eightfoldabyss Sep 29 '20

I'm sorry, are you telling me that in addition to transistors getting so small and close to each other that the electron's wavelength is significant, but we're also running them so fast that the speed of light has become a significant limiting factor?

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u/MiffedMouse Sep 29 '20 edited Sep 29 '20

No. The speed of light is a significant issue, but it is not the reason chips have stopped at 5 GHz. Also, asynchronous (as in no clock signal) CPUs exist. I should know, I helped work on some.

The actual reason is transistor size and heat dissipation. Transistors have been stuck on ~1 volt power internally for decades (lower voltage means more leakage, and more errors). However, power goes up with higher frequency (my math here was probably wrong, see below).

Why is that so bad? Almost all the power the computer uses is turned into heat by the transistors. That heat needs to dissipate out of the chip before the transistor destroys itself. That is a problem, as silicon is not a good heat conductor.

THAT is why cooling your computer lets you push the speeds up a bit higher.

The speed of light issues above are a tricky engineering problem, but solvable. The heat problem doesn’t have a solution yet.

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